1. Field of the Invention
This invention is concerned with blends of polymers and with tough films made from them.
2. Description of the Prior Art
It has been proposed to incorporate amorphous elastomers into various polymers, such as high density polyethylene, polypropylene, polystyrene, and polyvinyl chloride to increase toughness. In U.S. Pat. No. 3,261,889, it is disclosed that the incorporation of amorphous ethylene-propylene copolymer into low density polyethylene (LDPE) will increase environmental stress cracking resistance in wire coating applications.
It is the discovery of this invention, however, that amorphous ethylene-propylene copolymers will not increase the toughness of LDPE. In order to increase toughness of LDPE, an ethylene-propylene copolymer must have a certain amount of crystallinity and a specified ethylene content.